Hi, we got the maplins one from their b grade stock for 39.99.
It comes with the 'digi box' I have been reliably informed ( on this forum ) that they work well but ive not been able to set it up at home yet as we are surrounded by trees and cant get a clear view of the southern sky without standing in the middle of the road. I will be taking it on our next trip with the van, maybe i'll have a sympathetic neighbour who will help. There are lots of threads on this forum on the subject, this is one of them http://www.practicalcaravan.com/newforums/fm_messages.asp?FO=11&FM=413343
and this is a good site, crammed with information http://www.practicalcaravan.com/newforums/fm_messages.asp?FO=11&FM=413343